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Microbial Activity and Alkaline Hydrolysis in Thermal Environments
Biotransformation Kinetics of Thermophilic Hydrocarbon Degraders: Biodegradation rates of polycyclic aromatic hydrocarbons (PAHs) are typically low at mesophilic conditions and it is believed that the kinetics of degradation is controlled by PAH solubility and mass transfer rates. My group has focused on the interplay between mass transport and microbial reaction rates in thermal systems. Three thermophilic Geobacilli were isolated that grew on phenanthrene at 60°C and degraded the PAH more rapidly than other reported mesophiles. Our results show that while solubilization rates of PAHs are significantly enhanced at elevated temperatures, the biodegradation of PAHs under thermophilic conditions is still mass transfer limited due to enhanced degradation rates. Solubility tests were performed on phenanthrene, fluorene and fluoranthene at 20°C, 40°C and 60°C and, as expected, a significant increase in the equilibrium solubility concentration and of the rate of dissolution of these PAHs was observed with increasing temperature. A first order model was used to describe the PAH dissolution kinetics and the thermodynamic property changes associated with the dissolution process (enthalpy, entropy and Gibb’s free energy of solution) were evaluated. Further, other relevant thermodynamic properties for these PAHs, including the activity coefficients at infinite dilution, Henry’s law constants and octanol-water partition coefficients, were calculated in the temperature range 20-60°C. These studies are currently being extended to high pH conditions to take advantage of synergistic effects of hydrolytic chemical reactions that occur under alkaline conditions.
Microbial Activity in Thermoalkaline Springs: Alkaline hydrolysis is the degradation of organic compounds at high temperature and pH values of 8 and higher. Many compounds of military, national security, agricultural, and environmental significance can be destroyed by this reaction, including natural organic matter, explosives, propellants, nerve gasses, pesticides, renewable biomass, and chlorinated organics. Typically, microorganisms are not active at the high pH and temperature used in alkaline hydrolysis, but naturally occurring organisms exist in Yellowstone National Park that are highly adapted to these extreme conditions. Microorganisms known as alkaliphiles (interpreted literally as alkali loving) thrive and grow in high pH solutions (pH 9 to 11). In addition, thermophilic (heat loving) bacteria are active at temperatures ranging from 50°C to boiling. Organisms that flourish at both high pH and high temperature are called thermoalkaliphiles.
Through the use of these unique bacteria, a combined chemical and biological system could be used to quickly degrade hazardous compounds, even high explosives (e.g., TNT) and nerve gas agents. The thermoalkaliphilic system could be used for on-site treatment of a variety of compounds that are currently difficult to dispose. An example of a potential application envisioned includes a mobile, small-scale reactor for destruction of military explosives in the field. For domestic use, a reliable on-site treatment for farm pesticides would discourage the release of unused herbicides and insecticides. Further, studies on the unique capabilities of thermoalkaliphilic organisms will also help improve our understanding of the role of naturally occurring organic matter in thermoalkaline environments.
 Dr. Brent Peyton Sampling at a pH 10 hot spring near
Witch Creek in the Heart Lake Geyser Basin, YNP.
Current Laboratory Personnel:
John Aston, Ph.D. Student (john.aston@coe.montana.edu)
Rob Gardner, Ph.D. Student (rob.gardner@biofilm.montana.edu)
James Moberly, Ph.D. Student (james.moberly@coe.montana.edu)
Storm Shirley, Ph.D. Student (storm@montana.edu)
Michael VanEngelen, Ph.D. Student (mvanEngelen@coe.montana.edu)
Catherine VanEngelen, Ph.D. Student (calbaugh@coe.montana.edu)
Lisa Kirk, Ph.D. Student (lkirk@montana.com)
PUBLICATIONS
Viamajala, S. B.M. Peyton, L.A. Richards, J.N. Petersen. “Solubilization, Solution Equilibria, and Biodegradation of PAH's under Thermophilic Conditions”, Chemosphere, 66, 1094-1106, 2007.
COLABORATORS
William Apel, INL
Robin Gerlach, MSU
Matthew Fields, MSU
Keith Cooksey, MSU
Ross Carlson, MSU
Sridhar Viamajala, USU
Abigail Richards, MSU
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